Ink jet recording apparatus

Abstract

An ink jet recording apparatus includes a processing barrel for performing predetermined processing on a recording medium, transfer barrels disposed upstream and downstream of the processing barrel, two detection sensors facing the two transfer barrels, respectively, each detecting the pass of the recording medium, and a detecting circuit for detecting an abnormal pass of the recording medium from two output signals output from the two sensors and including two reverse logic delay timers, each delaying timing of a logic reverse to a detection logic of each of the two sensors with respect to the each output signals. Signal changes shorter than timer setting periods of the timers are removed from the output signals, respectively, to thereby prevent detection errors of the abnormal pass of the recording medium.

What is claimed is: 
     
       1. An ink jet recording apparatus that ejects droplets from nozzles of an ink jet head to record an image on a cut sheet-shaped recording medium, comprising:
 a processing barrel that performs predetermined processing on the recording medium while rotating with the recording medium retained on an outer circumferential surface thereof; 
 a transfer barrel that is disposed on an upstream side or a downstream side in a conveying direction of the recording medium with respect to the processing barrel so as to retain the recording medium on an outer surface thereof and transfer or receive the recording medium to or from the processing barrel by rotating with a leading end of the recording medium grasped; 
 a conveying unit that is disposed on the opposite side of the transfer barrel in the conveying direction of the recording medium with respect to the processing barrel so as to convey the recording medium from or to the processing barrel; 
 a first detection sensor and a second detection sensor that are provided so as to face the transfer barrel and the conveying unit to detect a pass of the recording medium; and 
 an abnormal pass detecting circuit that receives a first output signal output from the first detection sensor and a second output signal output from the second detection sensor so as to detect an abnormal pass of the recording medium from the received first and second output signals, 
 wherein the abnormal pass detecting circuit includes 
 a first reverse logic delay timer that delays timing of a logic reverse to a detection logic of the first detection sensor with respect to the first output signal, and 
 a second reverse logic delay timer that delays timing of a logic reverse to a detection logic of the second detection sensor with respect to the second output signal, and 
 wherein signal changes shorter than timer setting periods of the first and second reverse logic delay timers are removed from the first and second output signals, respectively, to thereby prevent detection errors of the abnormal pass of the recording medium by the abnormal pass detecting circuit. 
 
     
     
       2. The ink jet recording apparatus according to  claim 1 ,
 wherein the first and second detection sensors are sensors of which the detection logics become ON when the recording medium passes, and 
 wherein the first and second reverse logic delay timers are OFF-delay timers that add an OFF delay to the first and second output signals. 
 
     
     
       3. The ink jet recording apparatus according to  claim 1 ,
 wherein the first and second detection sensors are sensors of which the detection logics become OFF when the recording medium passes, and 
 wherein the first and second reverse logic delay timers are ON-delay timers that add an ON delay to the first and second output signals. 
 
     
     
       4. The ink jet recording apparatus according to  claim 1 ,
 wherein the first and second reverse logic delay timers are each configured to be capable of switching the timer setting period thereof, and 
 wherein the abnormal pass detecting circuit is configured to be capable of switching the detection timing at which the first and second detection signals indicating a pass of the recording medium are detected from the first and second output signals, respectively. 
 
     
     
       5. The ink jet recording apparatus according to  claim 1 ,
 wherein the timer setting period of each of the first and second reverse logic delay timers and the detection timing of the abnormal pass detecting circuit at which the first and second detection signals indicating a pass of the recording medium are detected from the first and second output signals, respectively, are switched in accordance with the length of the recording medium in the conveying direction and a conveying speed of the recording medium in the transfer barrel and the conveying unit. 
 
     
     
       6. The ink jet recording apparatus according to  claim 4 ,
 wherein the detection timing is delayed from the timing of the first output signal, indicating the pass of the recording medium by the timer setting period of the first reverse logic delay timer or longer. 
 
     
     
       7. The ink jet recording apparatus according to  claim 1 ,
 wherein the processing barrel performs the predetermined processing on the recording medium while retaining the recording medium on the outer circumferential surface thereof by rotating with the leading end of the recording medium grasped. 
 
     
     
       8. The ink jet recording apparatus according to  claim 1 ,
 wherein one of the transfer barrel and the conveying unit is a first transfer barrel that is disposed on the upstream side in the conveying direction of the recording medium with respect to the processing barrel so as to retain the recording medium on the outer surface thereof and transfer the recording medium to the processing barrel by rotating with the leading end of the recording medium grasped, and 
 wherein the other of the transfer barrel and the conveying unit is a second transfer barrel that is disposed on the downstream side in the conveying direction of the recording medium with respect to the processing barrel so as to retain the recording medium on the outer surface thereof and receive the recording medium from the processing barrel by rotating with the leading end of the recording medium grasped. 
 
     
     
       9. The ink jet recording apparatus according to  claim 8 ,
 wherein the processing barrel includes a first grasping unit that grasps the leading end of the recording medium, and is configured to rotate while retaining the recording medium of which the leading end is grasped by the first grasping unit on the outer circumferential surface thereof to thereby perform the predetermined processing on the recording medium, 
 wherein the first transfer barrel includes a second grasping unit that grasps the leading end of the recording medium, and is configured to rotate in contact with the processing barrel while retaining the recording medium of which the leading end is grasped by the second grasping unit on the outer surface thereof to thereby transfer the recording medium to the processing barrel by changing the state of the recording medium being grasped by the second grasping unit to the state of the recording medium being grasped by the first grasping unit of the processing barrel, and 
 wherein the second transfer barrel includes a third grasping unit that grasps the leading end of the recording medium, and is configured to rotate in contact with the processing barrel while retaining the recording medium of which the leading end is grasped by the third grasping unit on the outer surface thereof to thereby receive the recording medium from the processing barrel by changing the state of the recording medium being grasped by the first grasping unit of the processing barrel to the state of the recording medium being grasped by the third grasping unit. 
 
     
     
       10. The ink jet recording apparatus according to  claim 1 ,
 wherein the abnormal pass detecting circuit includes 
 a first detection circuit that outputs a first detection signal indicating the pass of the recording medium based on a predetermined detection timing signal from the first output signal which is output from the first detection sensor and processed by the first reverse logic delay timer, 
 a delay circuit that delays the first detection signal output from the first detection circuit by a predetermined setting period and outputs a delayed first detection signal, 
 a second detection circuit that outputs a second detection signal indicating the pass of the recording medium based on the predetermined detection timing signal from the second output signal which is output from the second detection sensor and processed by the second reverse logic delay timer, and 
 an abnormal pass determining circuit that determines the abnormal pass of the recording medium from the delayed first detection signal output from the delay circuit and the second detection signal output from the second detection circuit. 
 
     
     
       11. The ink jet recording apparatus according to  claim 10 ,
 wherein the abnormal pass determining circuit compares the delayed first detection signal with the second detection signal to determine the abnormal pass of the recording medium. 
 
     
     
       12. The ink jet recording apparatus according to  claim 10 ,
 wherein the abnormal pass determining circuit compares the delayed first detection signal and the second detection signal to determine that the pass of the recording medium is normal when both signals are identical and determine that the pass of the recording medium is abnormal when both signals are not identical. 
 
     
     
       13. The ink jet recording apparatus according to  claim 1 ,
 wherein the processing barrel is a drying barrel that rotates while retaining the recording medium on which the image is recorded by the ink jet head on the outer circumferential surface thereof so as to dry the image formed by the droplets on the recording medium. 
 
     
     
       14. The ink jet recording apparatus according to  claim 1 ,
 wherein the processing barrel is an image forming barrel that rotates while retaining the recording medium on the outer circumferential surface thereof to convey the recording medium and ejects droplets from the nozzles of the ink jet head to thereby form the image. 
 
     
     
       15. The ink jet recording apparatus according to  claim 1 ,
 wherein the first and second detection sensors are reflective sensors. 
 
     
     
       16. The ink jet recording apparatus according to  claim 1 ,
 wherein the first and second detection sensors detect the leading end of the recording medium.